1. Field of the Invention
The present invention relates to an illuminating device suitable for a room lamp for a vehicle and a method of fabricating the same, and more particularly, to a construction of an illuminating device using a light emitting diode (hereinafter, referred to as “LED”) as a light source and a method of fabricating the same.
2. Description of the Related Art
Conventionally, a map lamp or a room lamp for a vehicle includes a small-sized valve lamp (a miniature bulb) as a light source.
FIG. 8 is a cross-sectional view of an illuminating device known in the prior art. As can be apparently seen from FIG. 8, the illuminating device of the present example includes a circuit board 104 on which a socket 101 of a valve lamp, a required chip component 102 such as a resistor and an external connector 103 are mounted, a valve lamp 105 attached to the socket 101, a case 106 which also functions as a reflection plate, and a cover 107 which also functions as lens attached to the case 106.
Since a life span of the valve lamp 105 is short, for example, about 3000 hours, such an illuminating device needs to be constructed such that the cover 107 is detachable from the case 106 in preparation for a case where the valve lamp 105 is required to be replaced. Accordingly, the number of components is large, the construction thereof is complex, and a manufacturing cost is like to increase. Furthermore, since the valve lamp 105 has a large size and a heating value, and should be spaced apart from the cover 107 which functions as the lens at a predetermined distance, the thickness T of the apparatus increases and limits the flexibility of design in the vehicle. In addition, a user needs to replace the valve lamp 105, and thus, adding an increase in cost. In order to solve these defects, the present inventors have considered that an LED having a small heating value and a long life span be used as a light source of an illuminating device such as a room lamp or a map lamp, instead of the valve lamp 105.
Furthermore, in certain equipment for a vehicle, there has been a case where the LED is used as a light source of a dimming switch or a light source of a stop lamp in the vehicle (for example, see JP-A-2001-158290). However, the LED was not used as a light source of an illuminating device included in a vehicle, such as a room lamp or a map lamp.
However, it can not be sufficiently achieved to reduce the thickness of the illuminating device and manufacturing cost thereof by only using the LED instead of the valve lamp 105. That is, since the existing LED has low luminous intensity and a high directivity, a plurality of LEDs are required for obtaining the same lighting range as that of using the valve lamp 105, and thus, the number of the components and the number of the assembling processes increase. Furthermore, even in the case of using the LED, the circuit board and the cover which functions as the lens are necessary components, similar to the case of using the valve lamp 105. Further, since a reflecting plate needs to be included in some cases, if the members are composed similar to the case of using the valve lamp 105, reduction in the thickness of the illuminating device using the LED may be by only a gap provided between the light source and the cover 107 which functions as the lens, and the size difference between the light sources. Therefore, the reduction in thickness can not be significantly obtained.